As is well known in the art, such centralizers normally comprise a pair of axial spaced collars that are connected with a multiple of bow springs. The bow springs are bowed outwardly intermediate their ends so as to engage the wellbore. Such bow springs are equally spaced about the collars to enable the centralizer to maintain the conduit in the center of the well bore.
The attachment method for securing the bow springs to the collars is generally achieved through either a welding process or through a method where by the collars have been formed to receive the ends of the bow springs and firmly attach them to the collar. The centralizers that have been constructed using a welding process produce a low weight to volume ratio making them more costly to ship then centralizers that can be assembled at their point of use avoiding the welding process that may not readily be available. Centralizers that can be shipped in a disassembled state provides for assembly at destination and a subsequent reduction in shipping expenditure. Being in the disassembled condition also permits for different bow springs to be assembled within the collars to produce a variety of centralizers.
The materials used for the bow springs are hardened to produce the spring effect required for centering the conduit within the wellbore, the strength of such material being higher then that of the material used within the collar. Nominal strength material is used for the manufacture of the collar to economize the cost of goods.
Centralizers of a non-weld construction utilize openings within the collars to accept the bow springs that have a formed upset that projects into the collar opening. U.S. Pat. Nos. 4,909,322; 3,356,174 and 4,042,022 show centralizers of this type in which the collars are formed with an opening in the collar where a portion of the opening material has been retained to receive formed portions on the ends of the bow springs, and tabs on one or both sides of the openings which extend inwardly from the inner opening of the collars, so that when the formed section of the bow springs are so received, the tabs may be bent over the outer surfaces of the formed section to retain the ends of the springs against the inner surfaces of the collars, and thus hold the bent portions within the collar openings to secure the ends of the bow springs to the collars. The ends of the bow springs have been formed to be received within the opening of the collar. Within the opening of the collar there are portions of material that has been retained for use in securing the formed section of the bow spring ends within the opening of the collar, such portions of material are usually being opened ended and then bent into a position to achieve the locking of the formed section of the bow spring within the opening of the collar. The subsequent bending of the material may require multiple bends to achieve the locking of the formed bow spring section into the formed collar opening. It is therefore the object of this invention to provide a method of attaching the bow springs within the collar wherein the method of manufacture economizes on the amount of metal removed and bending of material used to secure the bow spring within the collar opening. Through a reduction of the collar material and bending of the same, strength in the subsequent attachment of the bow spring to the collar can be achieved. The reduction of material removal and forming of the collar material will economize the cost of goods.